From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: When a TCP segment is split up (to be sent through a TUN device with a small MTU) who should recalculate the checksum? Date: Fri, 15 Nov 2013 09:41:46 -0500 Message-ID: <528632AA.2090400@redhat.com> References: <5285E0BC.4090402@atlantech.com> <52862DBF.2060801@gmail.com> <5286305F.5060903@atlantech.com> Reply-To: vyasevic@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: John Hughes , Vlad Yasevich Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751185Ab3KOOl4 (ORCPT ); Fri, 15 Nov 2013 09:41:56 -0500 In-Reply-To: <5286305F.5060903@atlantech.com> Sender: netdev-owner@vger.kernel.org List-ID: On 11/15/2013 09:31 AM, John Hughes wrote: > On 15/11/13 15:20, Vlad Yasevich wrote: >> >> Can you check to see if you have the following patch in your kernel >> commit: 1cdbcb7957cf9e5f841dbcde9b38fd18a804208b >> Author: Simon Horman >> Date: Sun May 19 15:46:49 2013 +0000 >> >> net: Loosen constraints for recalculating checksum in skb_segment() >> >> >> This commit help if the forwarding system has to re-segment the data >> before transition. Especially if the receiving interface had GRO >> enabled with checksum offloading and the transmitting interface does >> not support checksum offloading. > > No, the Debian 3.10 kernel doesn't seem to have that commit: > > Around line 2859 in skbuff.c I see: > > if (fskb != skb_shinfo(skb)->frag_list) > continue; > Give it a try. It has helped me in similar situations. If it helps, we can get it into the stable tree. -vlad